Rotating electrical machine

ABSTRACT

The rotating electrical machine of the present invention includes: a magnet holder made of a non-magnetic material, which is formed by coupling a columnar portion for retaining the permanent magnet in a circumferential direction, and an annular portion for covering each axial side surface of the permanent magnet. The magnet holder includes, on an outer diameter side of both circumferential side surfaces of the columnar portion, engaging portions which engage with respective locking portions of the magnet cover, and includes, on an inner diameter side of each of both the circumferential side surfaces of the columnar portion, an extending portion extending along an inner peripheral surface of the magnet cover with a clearance (D) with respect to the inner peripheral surface of the magnet cover.

TECHNICAL FIELD

The present invention relates to a rotating electrical machine whichuses a permanent magnet as a stator.

BACKGROUND ART

There is known a rotating electrical machine which uses a permanentmagnet as a stator, in which consideration is made so that, even whenthe permanent magnet is damaged due to shock and the like from theoutside, a fragment of the permanent magnet does not cause rotationfailure of an armature serving as a rotor. Conventionally, as a rotatingelectrical machine of this type, there has been proposed a field deviceof a rotating electrical machine described in Patent Literature 1. Therotating electrical machine described in Patent Literature 1 includes amagnet cover formed of a thin plate, which covers an inner diameterportion (inner peripheral surface) and both circumferential sidesurfaces of the permanent magnet, and a magnet holder includingretaining portions interposed between the respective permanent magnets,for retaining the respective permanent magnets in a circumferentialdirection, and annular portions located at both axial end portions ofeach permanent magnet, for retaining the respective permanent magnets inan axial direction. The magnet cover includes locking portions nat bothcircumferential end portions thereof, and the retaining portion of themagnet holder includes an engaging portion which engages with thelocking portion of the magnet cover. The engaging portion engages withthe locking portion of the magnet cover, and thus the permanent magnetand the magnet cover are retained and fixed in an inner diameterdirection. Therefore, even when the permanent magnet is damaged, themagnet cover covers the inner peripheral surface and both thecircumferential side surfaces of the permanent magnet, and hence thefragment of the permanent magnet does not fly into the armature, androtation failure of the armature is prevented.

CITATION LIST Patent Literature

-   [PTL 1] JP 09-322443 A

SUMMARY OF INVENTION Technical Problem

The magnet cover forming the rotating electrical machine described inPatent Literature 1 is provided between the permanent magnet and thearmature serving as the rotor. In order to suppress performancereduction of the rotating electrical machine including this permanentmagnet and rotor, the magnet cover is formed of, for example, a thinplate made of a non-magnetic material and having a thickness of about0.1 mm. Therefore, when the magnet cover is deformed, there is a riskthat the magnet cover may come into contact with the rotor. Further, theengagement between the locking portion provided to the magnet cover andthe engaging portion provided to the retaining portion of the magnetholder determines the fitting position of the magnet cover. Therefore,when dimensional variations occur in radial length of the magnet coverand the like, there is a risk that the engagement between the magnetcover and the magnet holder becomes insufficient, or in some cases, theengagement between the magnet cover and the magnet holder is cancelled,which may cause movement of the magnet cover in the inner diameterdirection to cause contact to the rotor. In order to prevent deformationof the magnet cover and suppress dimensional variations of the magnetcover, measures such as strict management of the magnet cover arenecessary, which leads to a problem of increase in product cost.

Further, FIGS. 5 and 6 of Patent Literature 1 illustrate, as aconventional device, a rotating electrical machine in which a protrudingportion is provided to the retaining portion of the magnet holder on theinner diameter side thereof, for retaining the positions of thepermanent magnet and the magnet cover in the inner diameter direction.This conventional device does not include the engaging portion, and themagnet cover comes into contact with the protruding portion of themagnet holder, to thereby fix the magnet cover and the permanent magnetin a radial direction. Loads of the permanent magnet and the magnetcover act on the protruding portion, and hence there has been a problemin that the protruding portion is deformed to be brought into contactwith the rotor.

The present invention has been made to solve the above-mentionedproblems, and has an object to provide a rotating electrical machinewhich uses a permanent magnet and has further improved reliability, inwhich, even when deformation or dimensional variations of a magnet coveroccur, the magnet cover and the like do not come into contact with arotor, and a fragment of the permanent magnet and the magnet cover donot fly toward the rotor.

Solution to Problem

A rotating electrical machine according to the present inventionincludes a magnet holder made of a non-magnetic material, which isformed by coupling an annular portion for covering each axial sidesurface of a permanent magnet and a columnar portion provided betweenadjacent permanent magnets, for retaining the permanent magnet in acircumferential direction. The magnet holder includes, on an outerdiameter side of both circumferential side surfaces of the columnarportion, engaging portions which engage with locking portions providedto the magnet cover. The magnet holder includes, on an inner diameterside of each of both the circumferential side surfaces of the columnarportion, a first extending portion extending toward an inner peripheralsurface of the magnet cover with a clearance with respect to the innerperipheral surface of the magnet cover.

Advantageous Effects of Invention

According to the present invention, the columnar portion forming themagnet holder retains the permanent magnet in the circumferentialdirection. On the outer diameter side of both the circumferential sidesurfaces of the columnar portion, the engaging portions which engagewith the respective locking portions of the magnet cover are provided,and on the inner diameter side of each of both the circumferential sidesurfaces of the columnar portion, the first extending portion extendingtoward the inner peripheral surface of the magnet cover is provided witha clearance with respect to the inner peripheral surface of the magnetcover. With this configuration, it is possible to provide the rotatingelectrical machine with further improved reliability, in which, evenwhen deformation or dimensional variations of the magnet cover occur,the magnet cover and the like do not come into contact with the rotor,and the fragment of the permanent magnet and the magnet cover do not flytoward the rotor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A sectional view of a brushed motor 1 according to a firstembodiment of the present invention.

FIG. 2 A configuration view illustrating assembly of permanent magnets11 of the brushed motor 1 according to the first embodiment of thepresent invention.

FIG. 3 A perspective view of a magnet holder 13 illustrated in FIG. 2.

FIG. 4 A sectional view of the brushed motor 1 according to the firstembodiment of the present invention as viewed in an axial direction.

FIG. 5 An enlarged view of the vicinity of a columnar portion 13 a ofthe magnet holder 13 illustrated in FIG. 4.

FIG. 6 An enlarged view of the vicinity of the columnar portion 13 awhen a magnet cover 12 illustrated in FIG. 5 is deformed.

FIG. 7 An enlarged view of the vicinity of the columnar portion 13 awhen dimensional variations of an end surface portion 12 b of the magnetcover 12 illustrated in FIG. 5 occur.

FIG. 8 An enlarged view of the vicinity of a columnar portion 43 a of amagnet holder 43, which is a modified example of the magnet holder 13illustrated in FIG. 1.

FIG. 9 An enlarged view of the vicinity of a columnar portion 44 a of amagnet holder 44, which is another modified example of the magnet holder13 illustrated in FIG. 1.

FIG. 10 Sectional views of the magnet cover 12 illustrated in FIG. 4(FIG. 10( a)) and a magnet cover 33 which is a modified example of themagnet cover 12 (FIG. 10( b)), when the brushed motor 1 according to thefirst embodiment of the present invention is viewed in the axialdirection.

FIG. 11 A perspective view of a magnet cover 34 which is a modifiedexample of the magnet cover 12 illustrated in FIG. 2.

FIG. 12 A perspective view of a magnet cover 35 which is anothermodified example of the magnet cover 12 illustrated in FIG. 2.

FIG. 13 A side view when the magnet cover 35 illustrated in FIG. 12 isfitted to the magnet holder 13.

FIG. 14 A front view (FIG. 14( a)) of a magnet cover 36 which is amodified example of the magnet cover 12 illustrated in FIG. 4, and asectional view (FIG. 14( b)) taken along the line V-V of FIG. 14( a).

FIG. 15 A perspective view of a magnet holder 45 of a brushed motoraccording to a second embodiment of the present invention.

FIG. 16 A side view of the magnet holder 45 illustrated in FIG. 15.

FIG. 17 A perspective view of a magnet holder 46 of a brushed motoraccording to a third embodiment of the present invention.

FIG. 18 A side view of the magnet holder 46 illustrated in FIG. 17.

FIG. 19 A view illustrating a modified example of the magnet holder 46illustrated in FIG. 17.

FIG. 20 A configuration view illustrating assembly of permanent magnets15 of a brushed motor according to a fourth embodiment of the presentinvention.

FIG. 21 A side view of a magnet holder 48 illustrated in FIG. 20.

FIG. 22 A sectional view taken along the line VI-VI of FIG. 21.

FIG. 23 An enlarged view of the vicinity of a columnar portion 13 a ofthe magnet holder 48 illustrated in FIG. 21.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is a sectional view of a brushed motor 1, which is an example ofa rotating electrical machine, according to a first embodiment of thepresent invention. FIG. 2 is a configuration view illustrating assemblyof permanent magnets 11 of the brushed motor 1 according to the firstembodiment of the present invention. FIG. 3 is a perspective view of amagnet holder 13 illustrated in FIG. 2. Note that, in the followingdrawings, the same or corresponding parts are denoted by the samereference symbols.

As illustrated in FIG. 1, the brushed motor 1 includes a yoke 10 havinga bottomed cylindrical shape, four permanent magnets 11 made of aceramic-basedmaterial such as ferrite, which are arranged along an innerperipheral surface of the yoke 10 at predetermined intervals in acircumferential direction, and a rotor 20 which rotates on innerperipheral sides of the respective permanent magnets 11. A cornerportion 11 a of the permanent magnet 11, which is formed between aninner peripheral surface and a circumferential side surface thereof, hasa round shape, and a curvature radius of the corner portion 11 a is R3.The rotor 20 and a commutator 21 are fixed to a shaft 22. The shaft 22is supported in a freely rotatable state by a rear bearing 23 retainedin a bearing case portion 10 a provided in the yoke 10 and a frontbearing 24 retained in a bearing case portion 30 a provided in a housing30. Note that, in the first embodiment of the present invention,description is made of a case where the number of the permanent magnets11 is 4, but the number of the permanent magnets 11 is not limited to 4,and it is only required that a plurality of permanent magnets beprovided.

The inner peripheral surface and both circumferential side surfaces ofeach of the permanent magnets 11 are covered with a magnet cover 12formed of a thin plate made of a non-magnetic metal such asstainless-steel. As illustrated in FIG. 2, the magnet cover 12 includesan arc portion 12 a for protecting the inner peripheral surface of thepermanent magnet 11, end surface portions 12 b for protecting both thecircumferential side surfaces of the permanent magnet 11, and lockingportions 12 c bent at both end portions of the respective end surfaceportions 12 b. Further, a corner portion 12 d formed between the arcportion 12 a (inner peripheral surface of the magnet cover 12) and theend surface portion 12 b (circumferential side surface of the magnetcover 12) has a round shape, and a curvature radius of the cornerportion 12 d is R2.

Further, the permanent magnet 11 is retained at the inner peripheralsurface of the yoke 10 by the magnet holder 13 made of a non-magneticmaterial (for example, made of a resin). As illustrated in FIG. 2, themagnet holder 13 is formed by coupling, by integral molding, columnarportions 13 a each provided between adjacent permanent magnets 11, forretaining and fixing the permanent magnets 11 in the circumferentialdirection by press-fitting and the like, and annular portions 13 b forcovering both axial side surfaces of each of the permanent magnets 11.When the locking portions 12 c of the magnet cover 12 engage withengaging portions 13 c of the magnet holder 13, the magnet cover 12 ishoused in a space defined by the columnar portions 13 a and the annularportions 13 b of the magnet holder 13. Then, the permanent magnet 11 isinserted so that the arc portion 12 a of the magnet cover 12 covers theinner peripheral surface of the permanent magnet 11, and in addition,the end surface portions 12 b of the magnet cover 12 cover both thecircumferential side surfaces of the permanent magnet 11. In thismanner, the permanent magnet 11 is fitted to the inner peripheralsurface of the yoke 10 (see FIG. 1).

FIG. 4 is a sectional view of the brushed motor 1 according to the firstembodiment of the present invention as viewed in the axial direction.FIG. 5 is an enlarged view of the vicinity of the columnar portion 13 aof the magnet holder 13 illustrated in FIG. 4. As illustrated in FIG. 5,on the yoke 10 side of the columnar portion 13 a, that is, on an outerdiameter side of both the circumferential side surfaces thereof, theengaging portions 13 c which engage with the respective locking portions12 c of the magnet cover 12 are provided. Further, on the rotor 20 sideof the columnar portion 13 a, that is, on an inner diameter side of boththe circumferential side surfaces thereof, there is provided extendingportions 13 d each extending toward the inner peripheral surface of themagnet cover 12. A clearance D is provided between the extending portion13 d and the inner peripheral surface of the magnet cover 12, andnormally, the extending portion 13 d does not come into contact with themagnet cover 12. A corner portion 13 e formed between thecircumferential side surface of the columnar portion 13 a and theextending portion 13 d has a round shape, and a curvature radius of thecorner portion 13 e is R1. R1, R2, and R3 establish the relationship ofR1<R2<R3. Further, a corner portion 13 f formed between thecircumferential side surface of the columnar portion 13 a and theengaging portion 13 c is chamfered. Note that, the gap dimension betweenthe engaging portion 13 c of the magnet holder 13 and the innerperipheral surface of the yoke 10 is C.

In the brushed motor 1 according to the first embodiment of the presentinvention, which is configured as described above, the permanent magnets11 are retained and fixed between the magnet cover 12 and the yoke 10.When the locking portions 12 c of the magnet cover 12 engage with theengaging portions 13 c of the magnet holder 13, the fitting position ofthe magnet cover 12 is determined. Thus, the magnet cover 12 does notmove in the inner diameter direction any further, and hence the magnetcover 12 does not come into contact with the rotor 20, which preventsthe rotation failure of the rotor 20.

Further, for example, in a case where a part of the arc portion 12 a ofthe magnet cover 12 is significantly deformed as illustrated in FIG. 6,the deformed position (part A in FIG. 6) moves in the inner diameterdirection, but the deformed position comes into contact with theextending portion 13 d of the magnet holder 13, which prevents furthermovement of the magnet cover 12 in the inner diameter direction.Therefore, the magnet cover 12 does not come into contact with the rotor20, and it is possible to prevent the rotation failure of the rotor 20.Further, as described above, the permanent magnet 11 is retained andfixed by the columnar portions 13 a of the magnet holder 13 in thecircumferential direction, and is retained and fixed to the innerperipheral surface of the yoke 10 by the magnetic force of the permanentmagnet 11. Therefore, even when the magnet cover 12 is deformed and thedeformed position comes into contact with the extending portion 13 d ofthe magnet holder 13, a load of the permanent magnet 11 does not act onthe extending portion 13 d, and hence the extending portion 13 d is notdeformed. Therefore, the extending portion 13 d does not come intocontact with the rotor 20, and it is possible to prevent the rotationfailure of the rotor 20. Therefore, even when the magnet cover 12 isdeformed, the magnet cover 12 and the extending portion 13 d provided tothe magnet holder 13 do not come into contact with the rotor 20, and itis possible to prevent the rotation failure of the rotor 20. In a casewhere the degree of deformation of the arc portion 12 a of the magnetcover 12 is smaller than that in the case illustrated in FIG. 6, theclearance D is provided between the inner peripheral surface of themagnet cover 12 and the extending portion 13 d, and hence the magnetcover 12 does not come into contact with the extending portion 13 dbecause the clearance D is provided, and the force that acts on theextending portion 13 d can be reduced as compared to the case where theclearance D is absent.

Further, when there are variations in circumferential length of thelocking portion 12 c of the magnet cover 12, the part of the lockingportion 12 c for engagement is gradually reduced, and thus theengagement between the locking portion 12 c and the engaging portion 13c becomes shallow, but the magnet cover 12 moves in the inner diameterdirection while maintaining the engagement between the locking portion12 c and the engaging portion 13 c. The magnet cover 12 moves in theinner diameter direction until a part of the arc portion 12 a of themagnet cover 12, which is close to the end surface portion 12 b, comesinto contact with the extending portion 13 d of the magnet holder 13,but even in this case, as long as the engagement between the lockingportion 12 c and the engaging portion 13 c is maintained, the magnetcover 12 does not come into contact with the rotor 20 as describedabove. However, when larger variations occur and, for example, asillustrated in FIG. 7, the locking portion 12 c does not engage with theengaging portion 13 c, the magnet cover 12 moves in the inner diameterdirection up to a position at which the part of the arc portion 12 a ofthe magnet cover 12, which is close to the end surface portion 12 b,comes into contact with the extending portion 13 d (see part B of FIG.7). However, the magnet cover 12 does not move in the inner diameterdirection any further. Therefore, the magnet cover 12 does not come intocontact with the rotor 20, and it is possible to prevent the rotationfailure of the rotor 20. Further, from the same reasons as describedabove, even when the magnet cover 12 comes into contact with theextending portion 13 d of the magnet holder 13, the extending portion 13d is not deformed. Therefore, the magnet cover 12 and the extendingportion 13 d do not come into contact with the rotor 20, and it ispossible to prevent the rotation failure of the rotor 20.

From the description above, it can be said that the extending portion 13d of the magnet holder 13 restricts the position of the magnet cover 12so that the magnet cover 12 does not move in the inner diameterdirection with respect to the position at which the magnet cover 12comes into contact with the extending portion 13 d, and plays a role asa stopper for suppressing the movement of the magnet cover 12 in theinner diameter direction.

Further, as described above, the permanent magnet 11 is retained andfixed by the columnar portions 13 a of the magnet holder 13 in thecircumferential direction, and is retained and fixed to the innerperipheral surface of the yoke 10 by the magnetic force of the permanentmagnet 11. Therefore, even when the part of the arc portion 12 a of themagnet cover 12, which is close to the end surface portion 12 b, comesinto contact with the extending portion 13 d provided to the magnetholder 13, the extending portion 13 d is not deformed. Therefore, theextending portion 13 d does not come into contact with the rotor 20, andit is possible to prevent the rotation failure of the rotor 20.

As described above, the rotating electrical machine according to thefirst embodiment of the present invention includes the four permanentmagnets 11 arranged along the inner peripheral surface of thecylindrical yoke 10 at predetermined intervals in the circumferentialdirection, the magnet cover 12 for covering the inner peripheral surfaceand both the circumferential side surfaces of each of the permanentmagnets 11, the magnet cover 12 including the locking portions 12 c onouter sides of both the side surfaces, and the magnet holder 13 made ofa non-magnetic material, which is formed by coupling the annularportions 13 b for covering both the axial side surfaces of each of thepermanent magnets 11 and the columnar portions 13 a provided between theadjacent permanent magnets 11, for retaining the permanent magnets 11 inthe circumferential direction. The magnet holder 13 includes, on theouter diameter side of both the circumferential side surfaces of thecolumnar portion 13 a, the engaging portions 13 c which engage with therespective locking portions 12 c of the magnet cover 12, and includes,on the inner diameter side of both the circumferential side surfaces ofthe columnar portion 13 a, the extending portions 13 d each extendingtoward the inner peripheral surface of the magnet cover 12 with theclearance D with respect to the inner peripheral surface of the magnetcover 12. With this configuration, even when deformation or dimensionalvariations of the magnet cover 12 occur, the deformed position of themagnet cover 12 or the part of the arc portion 12 a of the magnet cover12, which is close to the end surface portion 12 b, comes into contactwith the extending portion 13 d, and thus the extending portion 13 dplays a role as a stopper for suppressing the movement of the magnetcover 12 in the inner diameter direction. In this manner, the magnetcover 12 does not move in the inner diameter direction any further.Therefore, it is possible to provide a rotating electrical machine withfurther improved reliability, in which the magnet cover 12 does not comeinto contact with the rotor 20 and the magnet cover 12 does not flytoward the rotor 20. Note that, the clearance D is provided between theinner peripheral surface of the magnet cover 12 and the extendingportion 13 d. Therefore, in the case where a part of the arc portion 12a of the magnet cover 12 is slightly deformed, the magnet cover 12 doesnot come into contact with the extending portion 13 d because theclearance D is provided, and the force that acts on the extendingportion 13 d can be reduced as compared to the case where the clearanceD is absent.

Note that, according to the first embodiment of the present invention,it is only required to newly provide the extending portion 13 d to theexisting magnet holder 13, and hence the number of parts does notincrease. Further, the extending portion 13 d is provided to thecolumnar portion 13 a of the magnet holder 13 made of a resin, and isprovided in a wide range on the inner diameter side of each of both thecircumferential side surfaces. Therefore, when the magnet holder 13 isformed by molding with a resin, the resin uniformly fills a region onthe inner diameter side of each of both the circumferential sidesurfaces of the columnar portion 13 a and between both the axial ends ofthe columnar portion 13 a to form the extending portion 13 d. Thus, theextending portion 13 d can be easily formed.

Further, the corner portion 13 e formed between the circumferential sidesurface and the extending portion 13 d of the columnar portion 13 a ofthe magnet holder 13 is formed into a round shape (curvature radius R1),and hence a root part of the extending portion 13 a, that is, the partof the extending portion 13 d, which is close to the corner portion 13e, may be formed to have a large thickness, and hence the strength ofthe extending portion 13 d can be improved. Further, the corner portion12 d formed between the inner peripheral surface (arc portion 12 a) andthe circumferential side surface (end surface portion 12 b) of themagnet cover 12 is formed into a round shape (curvature radius R2), andthe corner portion 11 a formed between the inner peripheral surface andthe circumferential side surface of the permanent magnet 11 is formedinto a round shape (curvature radius R3). In this case, the respectivecurvature radii R1, R2, and R3 are set to satisfy the relationship ofR1<R2<R3. Therefore, gaps are generated between the corner portion 11 aof the permanent magnet 11 and the corner portion 12 d of the magnetcover 12 and between the corner portion 12 d of the magnet cover 12 andthe corner portion 13 e of the magnet holder 13, and even whenvariations occur in the curvature radius R2 of the magnet cover 12, itis possible to absorb the variations of the curvature radius of themagnet cover 12.

Further, in the rotating electrical machine according to the firstembodiment of the present invention, as illustrated in FIG. 8, it ispossible to increase the gap dimension so that a gap dimension C1between an engaging portion 43 c of a magnet holder 43 and the innerperipheral surface of the yoke 10 satisfies C1>C (see FIG. 5). Throughincrease of the gap dimension as described above, although a lockingportion 12′c of a magnet cover 12′ (see magnet cover 12 illustrated inFIG. 7 and the dotted lines of FIG. 8) comes into contact with the innerperipheral surface of the yoke 10, the locking portion 12 c of themagnet cover 12 (see the solid line of FIG. 8) illustrated in FIG. 8does not come into contact with the inner peripheral surface of the yoke10. Therefore, a load from the yoke 10 is not applied, and with the gapdimension C1, it is possible to absorb the dimensional variations of themagnet cover 12.

Further, in the rotating electrical machine according to the firstembodiment of the present invention, description is made of the casewhere the corner portion 11 a of the permanent magnet 11, the cornerportion 12 d of the magnet cover 12, and the corner portion 13 e of themagnet holder 13 each have a round shape. However, the present inventionis not limited to this case. For example, as illustrated in FIG. 9, acorner portion 14 a of a permanent magnet 14, a corner portion 32 d of amagnet cover 32, and a corner portion 44 e of a magnet holder 44 mayeach have an angular shape. Also in the case where such corner portions14 a, 32 d, and 44 e are provided, even when deformation or dimensionalvariations of the magnet cover 32 occur, an extending portion 44 d(first extending portion) plays a role as a stopper for restricting themovement of the magnet cover 32 in the inner diameter direction. Thus,it is possible to provide a rotating electrical machine with furtherimproved reliability, in which the magnet cover 32 does not come intocontact with the rotor 20 and the magnet cover 32 does not fly towardthe rotor 20.

Note that, in the rotating electrical machine according to the firstembodiment of the present invention, description is made of a case wherethe magnet cover 12 includes the locking portions 12 c bent at both theend portions of the end surface portions 12 b (see FIG. 10( a)), but thepresent invention is not limited to this case. The locking portions 12 care only required to be provided on the outer sides of both thecircumferential side surfaces of the permanent magnet 11, and forexample, even when locking portions 33 a as illustrated in FIG. 10( b)are provided, the locking portions 33 a of the magnet cover 33 canengage with the respective engaging portions 13 c of the magnet holder13. This engagement determines the fitting position of the magnet cover12, and thus the magnet cover 12 does not move in the inner diameterdirection any further. Therefore, the magnet cover 12 does not come intocontact with the rotor 20, and it is possible to prevent the rotationfailure of the rotor 20.

Further, in the rotating electrical machine according to the firstembodiment of the present invention, instead of the magnet cover 12, amagnet cover 34 illustrated in FIG. 11 may be fitted to the magnetholder 13. The magnet cover 34 illustrated in FIG. 11 includes endsurface portions 34 b bent in a direction parallel to the annularportion 13 b of the magnet holder 13 at both axial ends of an arcportion 34 a thereof, and thus the magnet cover 34 is formed into a boxshape. With use of the magnet cover 34 instead of the magnet cover 12,the end surface portion 34 b of the magnet cover 34 overlaps with a sidesurface of the annular portion 13 b of the magnet holder 13, whichcovers the permanent magnet 11, without a gap. Therefore, even when thepermanent magnet 11 is damaged, a fragment of the permanent magnet 11does not fly toward the rotor 20, and it is possible to provide arotating electrical machine with further improved reliability.

Further, in the rotating electrical machine according to the firstembodiment of the present invention, instead of the magnet cover 12, amagnet cover 35 illustrated in FIGS. 12 and 13 may be fitted to themagnet holder 13. In the magnet cover 35 illustrated in FIGS. 12 and 13,at a circumferential center portion of one side surface of an arcportion 35 a thereof, there is provided a protruding portion 35 bprotruding in the axial direction. With use of the magnet cover 35instead of the magnet cover 12, the protruding portion 35 b of themagnet cover 35 overlaps with the inner peripheral surface of theannular portion 13 b of the magnet holder 13, and the magnet cover 35overlaps with the side surface of the annular portion 13 b, which coversthe permanent magnet 11, without a gap. Therefore, even when thepermanent magnet 11 is damaged, the fragment of the permanent magnet 11does not fly toward the rotor 20, and it is possible to provide arotating electrical machine with further improved reliability.

Further, in the rotating electrical machine according to the firstembodiment of the present invention, instead of the magnet cover 12, amagnet cover 36 illustrated in FIG. 14 may be fitted to the magnetholder 13. The magnet cover 36 illustrated in FIG. 14 includes a platespring 36 b on one side surface of an arc portion 36 a thereof. With useof the magnet cover 36 instead of the magnet cover 12, when the magnetcover 36 is fitted to the magnet holder 13, due to the elastic change ofthe plate spring 36 b of the magnet cover 36, the magnet cover 36 andthe magnet holder 13 overlap with each other in the axial direction ofthe magnet cover 36 without a gap. Therefore, even when the permanentmagnet 11 is damaged, the fragment of the permanent magnet 11 does notfly toward the rotor 20, and it is possible to provide a rotatingelectrical machine with further improved reliability.

Second Embodiment

In the above-mentioned first embodiment, description is made of a casewhere, in the rotating electrical machine which uses the permanentmagnet, the first extending portion is provided on the inner diameterside of each of both the circumferential side surfaces of the columnarportion forming the magnet holder. In contrast, in a second embodimentof the present invention, a second extending portion is further providedin the first embodiment on the inner diameter side of a corner portion,which is formed by coupling the columnar portion and the annular portionforming the magnet holder. This case is described with reference toFIGS. 15 and 16. FIG. 15 is a perspective view of a magnet holder 45forming a brushed motor according to the second embodiment of thepresent invention. FIG. 16 is a side view of the magnet holder 45illustrated in FIG. 15 as viewed from a direction (radial direction) inwhich the permanent magnet 11 and the magnet cover 12 are inserted. Notethat, in the brushed motor according to the second embodiment of thepresent invention, components other than the magnet holder 45illustrated in FIG. 15 are the same as those of the brushed motor 1illustrated in FIG. 1, and hence detailed description thereof isomitted.

In FIGS. 15 and 16, on the inner diameter side of four corner portions45 a formed by coupling the columnar portions 13 a and the annularportions 13 b of the magnet holder 45, there are respectively providedextending portions 45 b (second extending portion) each extending towardthe inner peripheral surface of the magnet cover 12. In this case, asdescribed in the first embodiment, the magnet cover 12 is inserted intoa space formed by the columnar portions 13 a and the annular portions 13b of the magnet holder 13. Therefore, in design, the axial length of themagnet cover 12 is generally set to be slightly smaller than the axiallength of the columnar portion 13 a of the magnet holder 13. Then, whenthe magnet cover 12 is fitted to the magnet holder 13, a gap isgenerated between the magnet cover 12 and the magnet holder 13 in thefitting direction of the magnet cover 12. Therefore, there has been arisk that, for example, when the permanent magnet 11 is damaged, thefragment of the permanent magnet 11 flies toward the rotor 20 throughthe gap. However, in the second embodiment of the present invention, theextending portions 45 b are respectively provided on the inner diameterside of the four corner portions 45 a formed by coupling the columnarportions 13 a and the annular portions 13 b of the magnet holder 45, andhence each of the extending portions 45 b of the magnet holder 45overlaps with the corner portion 12 d formed between the arc portion 12a and the end surface portion 12 b of the magnet cover 12 (see FIG. 1)in the vicinity of each axial end of the corner portion 12 d without agap. Therefore, even when the permanent magnet 11 is damaged, thefragment of the permanent magnet 11 does not fly toward the rotor 20,and it is possible to provide a rotating electrical machine with furtherimproved reliability.

As described above, in the rotating electrical machine according to thesecond embodiment of the present invention, on the inner diameter sideof the corner portion 45 a formed by coupling the columnar portion 13 aand the annular portion 13 b of the magnet holder 45, the extendingportion 45 b extending toward the inner peripheral surface of the magnetcover 12 is provided. With this configuration, the extending portion 45b of the magnet holder 45 overlaps with the corner portion 12 d of themagnet cover 12 in the vicinity of each axial end of the corner portion12 d without a gap. Therefore, even when the permanent magnet 11 isdamaged, the fragment of the permanent magnet 11 does not fly toward therotor 20, and it is possible to provide a rotating electrical machinewith further improved reliability.

Note that, according to the second embodiment of the present invention,it is only required to newly provide the extending portions 13 d and 45b to the magnet holder 45, and hence similarly to the first embodimentof the present invention, the number of parts does not increase.Further, the extending portion 45 b is provided on the inner diameterside of the corner portion 45 a formed between the columnar portion 13 aand the annular portion 13 b of the magnet holder 45 made of a resin,and provided on the same curved surface as the extending portion 13 dprovided on the inner diameter side of each of both the circumferentialside surfaces of the columnar portion 13 a. Therefore, the rangeincluding the extending portions 13 d and 45 b can be formed with onemold. Accordingly, when the magnet holder 45 is formed by molding with aresin, the range to be filled with the resin becomes wider as comparedto the case described in the first embodiment of the present invention,in which the magnet holder 13 is formed by molding with a resin, to arange including the extending portions 13 d and 45 b. The resinuniformly fills a portion on the inner diameter side of the cornerportion 45 a at which the extending portion 45 b is formed as well, andthus the extending portions 13 d and 45 b are formed. In this manner,the extending portions 13 d and 45 b can be easily formed.

Further, in the rotating electrical machine according to the secondembodiment of the present invention, description is made of a case wherethe extending portions 45 b are provided to all of the four cornerportions 45 a, but the present invention is not limited to this case.The extending portion 45 b may be provided to at least one cornerportion 45 a. In this case, a portion of the magnet holder 45 at whichthe extending portion 45 b is provided with respect to a surface towhich the permanent magnet 11 is inserted in a space formed by thecolumnar portions 13 a and the annular portions 13 b of the magnetholder 13 overlaps, without a gap, with a portion of the corner portion12 d of the magnet cover 12 which is in the vicinity of each axial endof the corner portion 12 d and to be inserted with respect to theextending portion 45 b. Therefore, when the permanent magnet 11 isdamaged and the fragment thereof flies toward the vicinity of theportion at which the extending portion 45 b is provided, it is possibleto prevent the fragment of the permanent magnet 11 from flying towardthe rotor 20.

Further, in the rotating electrical machine according to the secondembodiment of the present invention, description is made of a case wherethe extending portion 45 b axially extending toward the inner peripheralsurface of the magnet cover 12 is provided, and no description is madeof presence and absence of a clearance between the extending portion 45b and the inner peripheral surface of the magnet cover 12. The clearancemay be provided, or the extending portion 45 b may be brought intocontact with the inner peripheral surface of the magnet cover 12. Whenthe extending portion 45 b is brought into contact with the innerperipheral surface of the magnet cover 12, in addition to the engagementbetween the engaging portion 13 c of the magnet holder 45 and thelocking portion 12 c of the magnet cover 12, the extending portion 45 bprovided to the magnet holder 45 can be used to retain the magnet cover12, and hence the retaining force of the magnet holder 45 is improved.

Further, in the second embodiment of the present invention, similarly tothe description in the first embodiment, instead of the magnet cover 12,any one of the magnet cover 34 illustrated in FIG. 11, the magnet cover35 illustrated in FIG. 12, and the magnet cover 36 illustrated in FIG.14 may be fitted to the magnet holder 13. When any one of the magnetcovers 34 to 36 is used instead of the magnet cover 12, a part of eachmagnet cover (34, 35, or 36) and a part of the magnet holder 13 overlapwith each other without a gap. Therefore, even when the permanent magnet11 is damaged, the fragment of the permanent magnet 11 does not flytoward the rotor 20 through the overlapped part, and it is possible toprovide a rotating electrical machine with further improved reliability.

Third Embodiment

In the above-mentioned second embodiment, description is made of a casewhere, in the rotating electrical machine which uses the permanentmagnet, the first extending portion is provided on the inner diameterside of each of both the circumferential side surfaces of the columnarportion forming the magnet holder, and the second extending portion isfurther provided on the inner diameter side of the corner portion formedby coupling the columnar portion and the annular portion forming themagnet holder. In contrast, in a third embodiment of the presentinvention, description is made with reference to FIGS. 17 and 18 of acase where, in the first embodiment, on an inner diameter side of a sidesurface of the annular portion, which covers the permanent magnet, thereis further provided a third extending portion axially extending towardthe inner peripheral surface of the magnet cover. FIG. 17 is aperspective view of a magnet holder 46 forming a brushed motor accordingto the third embodiment of the present invention. FIG. 18 is a side viewof the magnet holder 46 illustrated in FIG. 17 as viewed from adirection (radial direction) in which the permanent magnet 11 and themagnet cover 12 are inserted. Note that, in the brushed motor accordingto the third embodiment of the present invention, components other thanthe magnet holder 46 illustrated in FIG. 17 are the same as those of thebrushed motor 1 illustrated in FIG. 1, and hence detailed descriptionthereof is omitted.

In FIGS. 17 and 18, on the inner diameter side of each of two sidesurfaces of the respective annular portions 13 b of the magnet holder46, which cover the permanent magnet 11 (for example, a shaded part inFIG. 17, the same applies to the other annular portion), there isprovided an extending portion 46 b (third extending portion) axiallyextending toward the inner peripheral surface of the magnet cover 12. Inthis case, as described in the second embodiment, when the extendingportions 45 b are provided on the inner diameter side of the four cornerportions 45 a formed by coupling the columnar portions 13 a and theannular portions 13 b of the magnet holder 45, the extending portions 45b overlap with the corner portions 12 d of the magnet cover 12 in thevicinity of both the axial ends of the corner portions 12 d. Therefore,the overlapping part can prevent the fragment of the permanent magnet 11from flying toward the rotor 20. However, the extending portion 45 bdoes not overlap with portions of the magnet cover 12 other than thevicinity of both the axial ends of the corner portions 12 d, and, forexample, at a circumferential center portion of the annular portion 13b, a gap is generated between the magnet cover 12 and the magnet holder45. Therefore, when the permanent magnet 11 is damaged, the fragment ofthe permanent magnet 11 flies toward the rotor 20 through the gap insome cases. In contrast, in the third embodiment of the presentinvention, on the inner diameter side of the side surface of the annularportion 13 b of the magnet holder 46, which covers the permanent magnet11, the extending portion 46 b is provided, and thus the extendingportion 46 b of the magnet holder 46 overlaps with the arc portion 12 aof the magnet cover 12 at each axial end of the arc portion 12 a withouta gap. Therefore, even when the permanent magnet 11 is damaged, thefragment of the permanent magnet 11 does not fly toward the rotor 20,and it is possible to provide a rotating electrical machine with furtherimproved reliability.

As described above, in the rotating electrical machine according to thethird embodiment of the present invention, on the inner diameter side ofeach of the two side surfaces of the respective annular portions 13 b,which cover the permanent magnet 11, the extending portion 46 b isprovided. With this configuration, the extending portion 46 b of themagnet holder 46 overlaps with the arc portion 12 a of the magnet cover12 at each axial end of the arc portion 12 a without a gap. As a result,even when the permanent magnet 11 is damaged, the fragment of thepermanent magnet 11 does not fly toward the rotor 20, and it is possibleto provide a rotating electrical machine with further improvedreliability. Note that, according to the third embodiment of the presentinvention, it is only required to newly provide the extending portions13 d and 46 b to the magnet holder 46, and hence similarly to the firstembodiment of the present invention, the number of parts does notincrease.

Note that, in the rotating electrical machine according to the thirdembodiment of the present invention, description is made of a casewhere, on the inner diameter side of each of the two side surfaces ofthe respective annular portions 13 b, which cover the permanent magnet11, the extending portion 46 b is provided. However, the presentinvention is not limited to this case, and the extending portion 46 bmay be provided on the inner diameter side of any one of the sidesurfaces. Alternatively, as illustrated in FIG. 19, on the innerdiameter side of one side surface of the annular portion 13 b, theextending portion 46 b described in the third embodiment of the presentinvention may be provided, and regarding the other side surface, asdescribed in the second embodiment of the present invention, on theinner diameter side of the corner portions 45 a formed between thecolumnar portions 13 a and the annular portion 13 b, the extendingportions 45 b (second extending portion) may be provided. As describedabove, when the extending portions 45 b and 46 b are provided to amagnet holder 47, the portions (45 b and 46 b) of the magnet holder 47at which the extending portions are provided overlap with the cornerportions 12 d or the arc portion 12 a of the magnet cover 12 at bothaxial ends thereof without a gap. Therefore, even when the permanentmagnet 11 is damaged, in a case where the fragment of the permanentmagnet 11 flies toward the vicinity of the portion at which theextending portion is provided, it is possible to prevent the fragment ofthe permanent magnet 11 from flying toward the rotor 20.

Further, in the rotating electrical machine according to the thirdembodiment of the present invention, description is made of a case wherethe extending portion 46 b axially extending toward the inner peripheralsurface of the magnet cover 12 is provided, and no description is madeof presence and absence of a clearance between the extending portion 46b and the inner peripheral surface of the magnet cover 12. The clearancemay be provided, or the extending portion 46 b may be brought intocontact with the inner peripheral surface of the magnet cover 12. Whenthe extending portion 46 b is brought into contact with the innerperipheral surface of the magnet cover 12, in addition to the engagementbetween the engaging portion 13 c of the magnet holder 46 and thelocking portion 12 c of the magnet cover 12, the extending portion 46 bprovided to the magnet holder 46 can be used to retain the magnet cover12, and hence the retaining force of the magnet holder 46 is improved.

Further, in the third embodiment of the present invention, similarly tothe description in the first embodiment, instead of the magnet cover 12,any one of the magnet cover 34 illustrated in FIG. 11, the magnet cover35 illustrated in FIG. 12, and the magnet cover 36 illustrated in FIG.14 may be fitted to the magnet holder 13. When any one of the magnetcovers 34 to 36 is used instead of the magnet cover 12, a part of eachmagnet cover (34, 35, or 36) and apart of the magnet holder 13 overlapwith each other without a gap. Therefore, even when the permanent magnet11 is damaged, the fragment of the permanent magnet 11 does not flytoward the rotor 20 through the overlapped part, and it is possible toprovide a rotating electrical machine with further improved reliability.

Fourth Embodiment

In the rotating electrical machine according to each of theabove-mentioned first to third embodiments, the permanent magnets areonly required to be arranged along the inner peripheral surface of theyoke at predetermined intervals in the circumferential direction, andthe shape of the permanent magnet has not been referred to. In contrast,in a fourth embodiment of the present invention, description is madewith reference to FIGS. 20 to 23 of a case where, in the first to thirdembodiments, the radial thickness of the permanent magnet is larger at acircumferential center portion thereof than at both the circumferentialend portions thereof. FIG. 20 is a configuration view illustratingassembly of permanent magnets 15 forming a brushed motor according tothe fourth embodiment of the present invention. FIG. 21 is a side viewof a magnet holder 48 illustrated in FIG. 20 as viewed from a direction(radial direction) in which the permanent magnet 15 and the magnet cover12 are inserted. FIG. 22 is a sectional view taken along the line VI-VIof FIG. 21, and a magnet cover 37 when the magnet cover 37 is fitted tothe magnet holder 48 is illustrated by a dotted line. Further, FIG. 23is an enlarged view of the vicinity of the columnar portion 13 a of themagnet holder 48 illustrated in FIG. 22. Note that, in the brushed motoraccording to the fourth embodiment of the present invention, componentsother than the permanent magnet 15, the magnet cover 37, and the magnetholder 48 illustrated in FIG. 20 are the same as those in the brushedmotor 1 illustrated in FIG. 1, and hence detailed description thereof isomitted.

The permanent magnet 15 is a permanent magnet similar to that describedin the above-mentioned first embodiment and is made of a ceramic-basedmaterial such as ferrite. As illustrated in FIG. 20, the magnet holder48 has a vertical sectional shape as viewed from the axial direction, inwhich a thickness h1 of the circumferential center portion is largerthan a thickness h2 of both the circumferential end portions (h1>h2).

In FIGS. 20 and 21, on the inner diameter side of one of side surfacesof the respective annular portions 13 b of the magnet holder 48, whichcover the permanent magnet 15, there is provided an extending portion 48a (third extending portion) axially extending toward the innerperipheral surface of the magnet cover 37. Regarding the other sidesurface, as described in the second embodiment of the present invention,two corner portions 45 a are formed by coupling the columnar portions 13a and the annular portion 13 b of the magnet holder 48, and on the innerdiameter side of the corner portions 45 a, there are provided extendingportions 45 b (second extending portion) extending toward the innerperipheral surface of the magnet cover 12. The length of the extendingportion 48 a extending in the axial direction is not constant in thecircumferential direction, and as illustrated in FIG. 21, a length a1 ofthe circumferential center portion is smaller than a length a2 of boththe circumferential end portions (a1<a2). In this case, as described inthe third embodiment, the extending portion 48 a is provided on theinner diameter side of one of the side surfaces of the respectiveannular portions 13 b, which cover the permanent magnet 15, and thus theextending portion 48 a of the magnet holder 48 overlaps, without a gap,with an axial end of an arc portion 37 a of the magnet cover 37 on aside at which the extending portion 48 a is provided. Therefore, evenwhen the permanent magnet 15 is damaged, the fragment of the permanentmagnet 15 does not fly toward the rotor 20, and it is possible toprovide a rotating electrical machine with further improved reliability.In this case, each circumferential end portion of the extending portion48 a is formed continuously with the extending portion 13 d provided tothe columnar portion 13 a, and hence deformation with respect to a forcein the radial direction is small (rigidity is large). However, thecircumferential center portion of the extending portion 48 a has asmaller rigidity than both the circumferential end portions describedabove, and hence when the length of the extending portion 48 a extendingin the axial direction is constant in the circumferential direction,there is a risk that the circumferential center portion of the extendingportion 48 a may be deformed or damaged. However, in the fourthembodiment of the present invention, regarding the length of theextending portion 48 a extending in the axial direction, the length a1of the circumferential center portion is set smaller than the length a2of both the circumferential end portions. Thus, the rigidity of thecircumferential center portion of the extending portion 48 a increases,and therefore the circumferential center portion of the extendingportion 48 a is not deformed and it is possible to provide a rotatingelectrical machine with further improved reliability.

Further, as illustrated in FIG. 22, the magnet cover 37 is fitted to themagnet holder 48. At this time, an air gap G is provided between thecircumferential center portion of the inner peripheral surface of themagnet cover 37 and the rotor 20, and a gap S is provided between adistal end portion of the inner peripheral surface of the extendingportion 13 d and the rotor 20. The gap S has a dimension larger thanthat of the air gap G (S>G). Further, the permanent magnet 15 isinserted so that the arc portion 37 a of the magnet cover 37 covers theinner peripheral surface of the permanent magnet 15, in addition, sothat the end surface portions 12 b of the magnet cover 37 cover both thecircumferential side surfaces of the permanent magnet 15. As a result,positional relationships as illustrated in FIG. 22 are obtained. In thiscase, the air gap G is set depending on characteristics necessary forthe rotating electrical machine, and is set by providing a clearance sothat the magnet cover 37 covering the permanent magnet 15 does not comeinto contact with the rotor 20. Therefore, it is necessary to set thegap S between the distal end portion of the inner peripheral surface ofthe extending portion 13 d and the rotor 20 to be larger than the airgap G. Therefore, S>G is satisfied, and S is set as G+α. Further, bothof the yoke 10 and the rotor 20 are concentrically formed. Therefore,the length from the yoke 10 to the rotor 20 is constant at both of thecircumferential center portion and each circumferential end portion ofthe permanent magnet 15. When a distance obtained by adding the radialthickness of the extending portion 13 d and the clearance between theextending portion 13 d and the inner peripheral surface of the magnetcover 37 is represented by D1 (see FIG. 23), and the gap between theinner peripheral surface of the yoke 10 and the outer peripheral surfaceof the permanent magnet 15 and the gap between the inner peripheralsurface of the permanent magnet 15 and the outer peripheral surface ofthe magnet cover 37 are not considered, the length from the yoke 10 tothe rotor 20 is represented by G+h1 at the circumferential centerportion of the permanent magnet 15, and is represented by S+D1+h2 atboth the circumferential end portions thereof. In this case, asdescribed above, the permanent magnet 15 has a vertical sectional shapeas viewed from the axial direction, in which the thickness h1 of thecircumferential center portion is larger than the thickness h2 of boththe circumferential end portions. When h1 is set as h2+β, the lengthfrom the yoke 10 to the rotor 20 is represented by G+(h2+β)=(G+α)+D1+h2,which may be represented by β=α+D1 when being arranged. This expressionrepresents that, regarding the radial thickness of the permanent magnet15, the thickness h2 of both the circumferential end portions is formedso as to be smaller by β than the thickness h1 of the circumferentialcenter portion, and this reduced thickness is equal to a distanceobtained by adding the thickness of the extending portion 13 d, theclearance D1 between the extending portion 13 d and the inner peripheralsurface of the magnet cover 37, and the clearance between the extendingportion 13 d and the rotor 20. With this configuration, it is possibleto provide a rotating electrical machine capable of effectively securingthe strength of the extending portion 13 d provided to the magnet holder48 while securing the air gap G including the clearance between themagnet cover 37 and the rotor 20.

As described above, in the rotating electrical machine according to thefourth embodiment of the present invention, an extending portion 48 b isprovided on the inner diameter side of each of the two side surfaces ofthe respective annular portion 13 b, which cover the permanent magnet11, and the length of the extending portion 48 b extending in the axialdirection is set so that the length a1 of the circumferential centerportion is smaller than the length a2 of both the circumferential endportions. Thus, the rigidity of the circumferential center portion ofthe extending portion 48 b increases, and hence the circumferentialcenter portion of the extending portion 48 a is not deformed and it ispossible to provide a rotating electrical machine with further improvedreliability. Note that, according to the fourth embodiment of thepresent invention, it is only required to newly provide the extendingportions 13 d, 45 b, and 48 b to the magnet holder 48, and hencesimilarly to the first embodiment of the present invention, the numberof parts does not increase.

Further, in the rotating electrical machine according to the fourthembodiment of the present invention, regarding the radial thickness ofthe permanent magnet 15, the thickness of the h1 of the circumferentialcenter portion is set larger than the thickness h2 of both thecircumferential end portions, and in addition, the gap S between thedistal end portion of the inner peripheral surface of the extendingportion 13 d and the rotor 20 has a dimension larger than that of theair gap G between the circumferential center portion of the innerperipheral surface of the magnet cover 37 and the rotor 20. Therefore,it is possible to provide a rotating electrical machine capable ofeffectively securing the strength of the extending portion 13 d providedto the magnet holder 48 while securing the air gap G including theclearance between the magnet cover 37 and the rotor 20.

Further, in the rotating electrical machine according to the fourthembodiment of the present invention, description is made of a case wherethe extending portion 46 b axially extending toward the inner peripheralsurface of the magnet cover 37 is provided, and no description is madeof presence and absence of a clearance between the extending portions 45b and 46 b and the inner peripheral surface of the magnet cover 37. Theclearance may be provided, or the extending portions 45 b and 46 b maybe brought into contact with the inner peripheral surface of the magnetcover 37. When the extending portions 45 b and 46 b is brought intocontact with the inner peripheral surface of the magnet cover 37, inaddition to the engagement between the engaging portion 13 c of themagnet holder 48 and the locking portion 12 c of the magnet cover 37,the extending portions 45 b and 46 b provided to the magnet holder 48can be used to retain the magnet cover 37, and hence the retaining forceof the magnet holder 48 is improved.

Further, in the fourth embodiment of the present invention, similarly tothe description in the first embodiment, instead of the magnet cover 37,any one of the magnet cover 34 illustrated in FIG. 11, the magnet cover35 illustrated in FIG. 12, and the magnet cover 36 illustrated in FIG.14 may be fitted to the magnet holder 13. When any one of the magnetcovers 34 to 36 is used instead of the magnet cover 12, a part of eachmagnet cover (34, 35, or 36) and a part of the magnet holder 13 overlapwith each other without a gap. Therefore, even when the permanent magnet11 is damaged, the fragment of the permanent magnet 11 does not flytoward the rotor 20 through the overlapped part, and it is possible toprovide a rotating electrical machine with further improved reliability.

REFERENCE SIGNS LIST

1 brushed motor (rotating electrical machine), 10 yoke, 10 a, 30 abearing case portion, 11, 14, 15 permanent magnet, 11 a, 12 d, 13 e, 14a, 32 d, 44 e, 45 a corner portion, 12, 32, 33, 34, 35, 36, 37 magnetcover, 12 a, 12′a, 32 a, 34 a, 35 a, 36 a, 37 a arc portion, 12 b, 12′b,34 b end surface portion, 12 c, 12′c, 33 a locking portion, 13, 43, 44,45, 46, 47, 48 magnet holder, 13 a, 43 a, 44 a columnar portion, 13 bannular portion, 13 c, 43 c engaging portion, 13 d, 44 d extendingportion (first extending portion), 13 f corner portion (chamferedportion), 20 rotor (armature), 21 commutator, 22 shaft, 23 rear bearing,24 front bearing, 30 housing, 35 b protruding portion, 36 b: platespring, 45 b extending portion (second extending portion), 46 b, 48 aextending portion (third extending portion), C, C1 gap dimension, D, D1clearance, G air gap, R1 curvature radius of corner portion 13 e, R2curvature radius of corner portion 12 d, R3 curvature radius of cornerportion 11 a, S gap.

1. A rotating electrical machine, comprising: a plurality of permanentmagnets arranged along an inner peripheral surface of a cylindrical yokeat predetermined intervals in a circumferential direction; a magnetcover for covering an inner peripheral surface and both circumferentialside surfaces of each of the plurality of permanent magnets, the magnetcover comprising locking portions on outer sides of both thecircumferential side surfaces; and a magnet holder made of anon-magnetic material, which is formed by coupling a columnar portionprovided between adjacent permanent magnets, for retaining the each ofthe plurality of permanent magnets in the circumferential direction, andan annular portion for covering each axial side surface of the each ofthe plurality of permanent magnets, wherein the magnet holder comprises,on an outer diameter side of both circumferential side surfaces of thecolumnar portion, engaging portions which engage with the respectivelocking portions of the magnet cover, and comprises, on an innerdiameter side of each of both the circumferential side surfaces of thecolumnar portion, a first extending portion extending toward an innerperipheral surface of the magnet cover with a clearance with respect tothe inner peripheral surface of the magnet cover.
 2. A rotatingelectrical machine according to claim 1, wherein: the columnar portionand the first extending portion of the magnet holder form a cornerportion having a round shape; and the following relationship isestablished,R1<R2<R3, where R1 represents a curvature radius of the corner portion,R2 represents a curvature radius of a corner portion formed between theinner peripheral surface and a circumferential side surface of themagnet cover, and R3 represents a curvature radius of a corner portionformed between the inner peripheral surface and each of both thecircumferential side surfaces of the each of the plurality of permanentmagnets.
 3. A rotating electrical machine according to claim 1, furthercomprising a rotor which rotates on an inner peripheral side of the eachof the plurality of permanent magnets, wherein: the each of theplurality of permanent magnets has a radial thickness set so that acircumferential center portion is thicker than both circumferential endportions; and a gap between a distal end portion of an inner peripheralsurface of the first extending portion and the rotor has a dimensionlarger than a dimension of an air gap between a circumferential centerportion of the inner peripheral surface of the magnet cover and therotor.
 4. A rotating electrical machine according to claim 1, whereinthe magnet holder further comprises, on an inner diameter side of eachcorner portion formed by coupling the columnar portion and the annularportion, a second extending portion extending toward the innerperipheral surface of the magnet cover.
 5. A rotating electrical machineaccording to claim 1, wherein the magnet holder further comprises, on aninner diameter side of a side surface of the annular portion, whichcovers corresponding one of the plurality of permanent magnets, a thirdextending portion axially extending toward the inner peripheral surfaceof the magnet cover.
 6. A rotating electrical machine according to claim5, wherein the third extending portion axially extending toward theinner peripheral surface of the magnet cover has a length set so that acircumferential center portion is smaller than both circumferential endportions.